Erich, yes, Texas does have many mines, but only a few are still active. Most of them are in far west texas, mercury/ cinabar, gypsum/potash, and many are abandoned, including a topaz and opal mine I know of. I don't know of any that are open to the public, like some are in other states. If you managed to get access to an abandoned one, you would be very lucky. Alot of them have become inhabited by bats also, and have been gated so that only the bats can use them for roosts.